The Red Emperor is the latest of a long dynasty of wizard-kings who rule the Lunar Empire, answerable only to their mother, the Red Moon goddess. They are immortal, in that no “natural” death can take them, although many have been slain in physical or magical combat (most notably in the Battle of Boldhome in 1602 and by Harrek the Berserk in 1607). Because they are a fanatical and warlike dynasty, many Moonsons have descended to earth to rule. Each appears identical and maintains the Imperial policies of his predecessor, so that it is claimed by many that one man has ruled for centuries.
It is worth noting that the Sartarites totally do not buy the whole Mask thing.